1. Field of the Invention
The invention relates to a pressure-fed journal bearing such as commonly used in a steam turbine or gas turbine engine.
2. Description of the Prior Art
The oil fed to a journal bearing in addition to decreasing the friction between the shaft and the bearing surface also removes heat from the bearing. There are generally a plurality of such bearings in a steam turbine unit which are commonly fed from an oil manifold, pressurized to maintain a sufficient quantity of flow through each bearing to remove the heat generated therein and provide the necessary lubrication.
There are several well known journal bearing designs, with each design generally having certain advantages. One well known phenomena associated with journal bearings is referred to as oil whip and generally is a form of vibration of the journal or shaft within the bearing due to turbulent oil action. To minimize oil whip, there are various bearing designs that tend to force or maintain the journal close to the center of the bearing to prevent such movement.
A presently used bearing design of the assignee of this application provides a journal bearing wherein an oil film is maintained over the 360.degree. interface of the shaft and the bearing surface. The oil inlet for this bearing is in a quadrant diametrically opposed to the quadrant of minimum oil film thickness determined by the load and direction of rotation. It is felt the inlet pressure of the oil on the journal, in concert with the load and direction of rotation will effectively reduce the oil whip to an acceptable level. However, in so doing, the oil is introduced in a radial direction to impinge upon the journal or upon the shaft in an area wherein there is no necessity for an oil film thickness for lubrication. Thus, in addition to the pressure of the manifold being maintained to deliver a sufficient quantity of oil at a generally high pressure inlet condition, additional work must be done by the shaft to transport the oil to the lower portion of the bearing where it is necessary to establish a lubricating film between the bearing and the shaft therein.
It is known that a partial arc sleeve, i.e. a journal bearing wherein the cover is relieved because it has no load carrying ability, has less bearing losses. Further, it is common in journal bearings to introduce the oil generally at the center of the bearing from whence it flows axially in both directions to circumferential troughs adjacent the bearing ends for drainage to a reservoir. This then determines that the oil film pressure is a maximum at the axial center and decreases axially in both directions to approach zero at the ends. Thus, in the axial direction, the journal or shaft is supported by a maximum oil film of limited axial extent.